chardet

What is chardet?

The chardet npm package is a character encoding detector library, which allows you to determine the encoding of a given piece of text or a file. It is based on the character detection component of the ICU (International Components for Unicode) project and can be useful when dealing with text data that does not have encoding information.

What are chardet's main functionalities?

Detecting encoding of a text buffer

This code reads a file and uses chardet to detect the encoding of its content. The 'detect' function takes a buffer and returns the name of the encoding it believes the text is in.

const chardet = require('chardet');
const fs = require('fs');

fs.readFile('/path/to/file', (err, data) => {
  if (err) throw err;
  const encoding = chardet.detect(data);
  console.log(encoding);
});

Detecting encoding with confidence

This code creates a buffer from a string and uses chardet's 'detectAll' function to get an array of possible encodings along with their confidence scores.

const chardet = require('chardet');

const buffer = Buffer.from('Some text with unknown encoding');
const result = chardet.detectAll(buffer);
console.log(result);

Detecting encoding of a file stream

This code creates a read stream from a file and uses chardet's 'detectStream' function to detect the encoding of the streamed content asynchronously.

const chardet = require('chardet');
const fs = require('fs');

const stream = fs.createReadStream('/path/to/file');
chardet.detectStream(stream).then(encoding => {
  console.log(encoding);
});

Other packages similar to chardet

iconv-lite

iconv-lite is a character encoding conversion library. Unlike chardet, which detects the encoding, iconv-lite is used to convert from one encoding to another. It supports many encodings and is often used in conjunction with chardet to first detect the encoding and then convert the text.

jschardet

jschardet is a port of the python library chardet. It serves the same purpose as the chardet npm package, which is to detect the character encoding of text. The main difference may be in the implementation details and the specific encodings supported by each library.

encoding

The encoding npm package is another library for encoding and decoding text. It provides a simpler API for converting between encodings but does not have the detection capabilities of chardet. It's often used when the encoding is already known.

README

chardet

Chardet is a character detection module written in pure JavaScript (TypeScript). Module uses occurrence analysis to determine the most probable encoding.

• Packed size is only 22 KB
• Works in all environments: Node / Browser / Native
• Works on all platforms: Linux / Mac / Windows
• No dependencies
• No native code / bindings
• 100% written in TypeScript
• Extensive code coverage

Installation

npm i chardet

Usage

To return the encoding with the highest confidence:

import chardet from 'chardet';

const encoding = chardet.detect(Buffer.from('hello there!'));
// or
const encoding = await chardet.detectFile('/path/to/file');
// or
const encoding = chardet.detectFileSync('/path/to/file');

To return the full list of possible encodings use analyse method.

import chardet from 'chardet';
chardet.analyse(Buffer.from('hello there!'));

Returned value is an array of objects sorted by confidence value in descending order

[
  { confidence: 90, name: 'UTF-8' },
  { confidence: 20, name: 'windows-1252', lang: 'fr' },
];

In browser, you can use Uint8Array instead of the Buffer:

import chardet from 'chardet';
chardet.analyse(new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0x6f]));

Working with large data sets

Sometimes, when data set is huge and you want to optimize performance (with a trade off of less accuracy), you can sample only the first N bytes of the buffer:

const encoding = await chardet.detectFile('/path/to/file', { sampleSize: 32 });

You can also specify where to begin reading from in the buffer:

const encoding = await chardet.detectFile('/path/to/file', {
  sampleSize: 32,
  offset: 128,
});

Working with strings

In both Node.js and browsers, all strings in memory are represented in UTF-16 encoding. This is a fundamental aspect of the JavaScript language specification. Therefore, you cannot use plain strings directly as input for chardet.analyse() or chardet.detect(). Instead, you need the original string data in the form of a Buffer or Uint8Array.

In other words, if you receive a piece of data over the network and want to detect its encoding, use the original data payload, not its string representation. By the time you convert data to a string, it will be in UTF-16 encoding.

Note on TextEncoder: By default, it returns a UTF-8 encoded buffer, which means the buffer will not be in the original encoding of the string.

Supported Encodings:

• UTF-8
• UTF-16 LE
• UTF-16 BE
• UTF-32 LE
• UTF-32 BE
• ISO-2022-JP
• ISO-2022-KR
• ISO-2022-CN
• Shift_JIS
• Big5
• EUC-JP
• EUC-KR
• GB18030
• ISO-8859-1
• ISO-8859-2
• ISO-8859-5
• ISO-8859-6
• ISO-8859-7
• ISO-8859-8
• ISO-8859-9
• windows-1250
• windows-1251
• windows-1252
• windows-1253
• windows-1254
• windows-1255
• windows-1256
• KOI8-R

Currently only these encodings are supported.

TypeScript?

Yes. Type definitions are included.

References

• ICU project http://site.icu-project.org/